<span class="math"><math><msup><mi></mi><mn>3</mn></msup><mtext>He</mtext><msup><mi></mi><mn>4</mn></msup><mtext>He</mtext></math></span> ratio,noble gas abundance and K-Ar dating of diamonds—An attempt to search for the records of early terrestrial history期刊界 All Journals 搜尽天下杂志传播学术成果专业期刊搜索期刊信息化学术搜索

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$^{3} He^{4} He$ ratio,noble gas abundance and K-Ar dating of diamonds—An attempt to search for the records of early terrestrial history

Authors:	M Ozima S Zashu O Nitoh

Institution:	1. Geophysical Institute, University of Tokyo, Tokyo 113, Japan;7. Faculty of Engineering, Tokyo University of Agriculture and Technology, Koganei-city, 184, Japan

Abstract:	The $^{3} He^{4} He$ ratios measured in 27 Southern Africa diamond stones, four from Premier Mine and the rest of unidentified origin, range from 4.2 × 10^?8 to 3.2 × 10^?4, with three stones above 1 × 10^?4. We conclude that the initial helium isotopic ratio ( $^{3} He^{4} He)_{0}$ in the earth was significantly higher than that of the planetary helium-A ( $^{3} He^{4} He = 1.42 × 10^{?4}$ ), but close to the solar helium ( $^{3} He^{4} He ? 4 × 10^{?4}$ ).The apparent K-Ar ages for the twelve diamonds of unidentified origin show enormously old age, indicating excess argon-40. $^{3} He^{4} He$ evolution in diamonds suggests that the diamonds with the high $^{3} He^{4} He$ ratio (>2 × 10^?4) may be as old as the earth.Noble gas elemental abundance in the diamonds relative to the air noble gas abundance shows monotonie decrease with a decreasing mass number.This paper discusses the implications of these observations on the early solar system and the origin of diamonds.

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